Process for producing color photographs



United States Patent US. CI. 9653 8 Claims ABSTRACT OF THE DISCLOSURE The present invention provides an improvement in a process for producing color photographs by the silver dye bleach method. The improvement comprises treating photographic layers containing gelatine, a metallizable azo dyestuff fast to dilfusion, being freed from metallic silver by oxidation, with a water soluble compound of a metal having an atomic number of at least 24 and at most 29. The photographs have an improved fastness to light which also is manifested by pure colors free from stain.

This is a continuation-in-part of our copending application Ser. No. 34,389, filed June 7, 1960, now abandoned.

The present invention provides an improvement in a process for producing color photographs by the silver dye bleach method. As is known, their poor fastness to light is a disadvantage of the known color photographs. This is particularly true of materials processed by the dyeforming development. It is, however, also true of the socalled silver bleaching out process in which the dyestuffs contained in the individual layers are bleached out depending on the quantity of silver produced photographically in the layer.

As will be explained hereinafter the unsatisfactory fastness to light of pictures produced by the silver dye bleaching method is attributable to various reasons. It can be substantially improved in the present process for making color photographs by the silver dye bleach method wherein a color image containing material, having at least one gelatine layer containing a metallizable azo dye and being resistant to diffusion, is freed from metallic silver by oxidation. The improvement comprises treating said material subsequent to said oxidation with a water soluble compound of a metal having an atomic number of at least 24 and at most 29 in an aqueous medium of pH 3.5 to 11.5.

Particularly advantageous results are in general obtained with compounds of cobalt, nickel and copper.

There may be used simple salts of the said heavy metals derived from an inorganic or organic acid, for example the chlorides, sulfates, nitrates, formates or acetates. Since, however, a strongly acidic reaction medium should not be used and the process is advantageously performed in an alkaline medium, it is of advantage to use a heavymetal compound from which at such a pH value no precipitate results, that is to say preferably a water-soluble heavy metal compound containing the heavy metal bound in complex union.

The heavy-metal atom may be present, for example, in the anion of a complex derived from an organic, colorless hydroxycarboxylic acid. As relevant examples may be mentioned the complexes consisting of an alkali metal salt or ammonium salt with a heavy metal salt of citric acid, lactic acid, tartaric acid or of a monocyclic orthohydroxycarboxylic acid of the benzene series such as 4- or 6-methyl-1-hydroxybenzene-2-carboxylic acid or preferably of salicylic acid not containing any further substituents.

Particularly suitable are also the heavy metal amine complex compounds derived from ammonia or a lower aliphatic amine such as methylamine, ethylamine, mono-, dior triethanolamine, or from a pyridine base such as pyridine itself or from a picoline or from an amino-carboxylic acid such as a glycine.

Instead of dissolving a complex compound obtained in known manner for the treatment of the photographic material in water or in another suitable solvent, it may in some cases be prepared immediately before use or made up into a stock solution, for example by adding to an aqueous solution of copper sulfate tartaric acid and then sodium hydroxide solution until a weakly alkaline reaction is achieved, or by treating the copper sulfate solution with excess aqueous ammonia.

The present process may be performed with for example, a monoazo, disazo or polyazo dyestufi which may be free from, or preferably may contain, groups imparting solubility in water, more especially sulfonic acid groups. The tint depends On the individual purpose so that dyestuffs to be used prefentially are those of yellow, cyan, and magenta tint of extreme purity. Owing to the fact that the photographic material has to satisfy requirements quite different from those arising in the case of dyed textile materials, the stability of the metal-dyestuff complexes in an aqueous medium at an elevated temperature is of minor importance so that there is no objection to using in the present case dyestuffs containing groups capable of forming metal complexes that are far too unstable for use in dyeing textile materials and accordingly produce complexes that are not fast to washmg.

Thus, for example, there are quite generally suitable dyestuffs that contain at least one hydroxyl group (including an enolizable ketomethylene group) in a vicinal position to an azo linkage. For the reasons given above the other vicinal position need not contain a substituent that participates in or promotes the complex formation. Thus, for example, the complex-forming azo dyestuff may contain an atomic grouping of the formula Apart from the azo dyestufis mentioned above there may be used with advantage also those which contain at least one azo linkage carrying a substituent in vicinal position to the other nitrogen atom, said substituent being capable of forming together with the hydroxyl group a complex heavy-metal compound. As examples of complex-forming groups of this composition may be mentioned ortho-hydroxy-ortho'-alkoxy groups, more especially the ortho-hydroxy-ortho'-methoxyazo group, the ortho-hydroxy-ortho-aminoazo group, the ortho-hydroxyortho-carboxymethoxy-azo group, the ortho-hydroxyortho'-carboxyazo grouping and the ortho:ortho'-dihydroxyazo grouping.

There may also be used dyestuffs in the case of which the complex may be formed, instead of at the substituents in vicinal positions to an azo linkage, for example, at an 8-hydroxyquinoline radical or more especially at a salicylic acid grouping. It will be readily understood that the dyestuifs may contain two or more identical or difierent groups capable of forming complexes.

A large number of dyestuffs suitable for the present process is known and they can be made by conventional, as such known methods.

According to the present process the treatment with the heavy-metal compound is performed at a pH value of at least 3.5, advantageously of at least 4 and of at most 11.5. At these pH values heavy-metal-dyestuif complexes are still stable, while in a more strongly acidic medium they decompose extensively or even completely, or are at best only formed in a minor amount. For this reason it is of advantage to per-form the treatment with the heavy-metal compound after an optional treatment in a strongly acidic medium.

In the case of some dyestuffs the after-treatment is accompanied by slight shift in tint. This shift must be taken into consideration in selecting the dyestuif to be used.

The present invention offers considerable advantages over the known processes. While very many dyestuffs that are fast to light are known, only some of them are suitable for use in the silver dye bleach process because they must satisfy numerous requirements arising from other aspects of the photographic process. Thus, for example, the dyestuffs to be used in the silver dye bleach process must be compatible with the individual constituents of the silver halide emulsion; they must satisfy certain spectral conditions, and they must lend themselves to bleaching out. Many dyestuffs that are fast to light are unsuitable because they have a strong desensitizing effect on the silver halide emulsion. The necessity of increasing the fastness to light is further emphasized by the fact that the fastness to light depends very much on the substratum so that, for example, certain dyestuffs that are fast to light when applied to cotton are much less fast to light in gelatine. More especially, the different additives required to be present in a gelatine emulsion or in a layer adjacent thereto such, for example as organic bases, which act as sensitizers or have the purpose of counteracting the tendency of the dyestuffs to diffuse, have a disadvantageous effect on the fastness to light of the dyestuffs in the finished image. Many of these additives are needed to be present only during the manufacture of the light-sensitive photographic material or during the development process, but they cannot always be washed out of the material; others, such, for example, as the Scission products of dyestuffs and filter dyestuffs, arise only during developing. The reduction of the light fastness to dyestuffs due to the presence of organic bases that cannot be washed out such, for example, as quaternary nitrogen bases or guanidine bases, can be annulled by an after-treatment with a heavy-metal compound. It is a moot point whether the increase in fastness to light is attributable to the mere presence of the heavy-metal compound in the layer or to the formation of dyestuffmetal complexes or to a reaction with any base present, or to a combination of several of these factors.

When a base is present for the purpose of increasing the resistance of the dye to diffusion during casting and NaOOO developing, the change in this base by forming a compound with the heavy-metal towards the end of the process is no longer disadvantageous since there is no need for the dyestuff to resist washing out in the finished image. There may also be added to the after-treatment bath besides the heavy-metal compound an organic base, for example a biguanide, whereby the resistance to diffusion is maintained without impairing the advantageous effect of the heavy-metal compound on the fastness to light.

After-treatment according to the present process not only enhances the fastness to light of the dyestuif as such, but it may also effect a chemical change in the substratum and in the additives so that they lose their harmful influence. The advantages in this connection are more especially that the fastness to light does not materialize until after the after-treatment, while during the manufacture of the photosensitive material and during its development the light fastness of the dyestuif need not be considered; as a matter of fact it is even possible to use measures that jeopardize the fastness to light, but that can be annulled or eliminated by the after-treatment. Inter alia, it is possible to incorporate in the layers dyestuffs that are at first free from heavy metal and thus have less fastness to light but which have better compatibility with the emulsion; by virtue of their constitution do not diffuse or can be made resistant to diffusion; lend themselves well to bleaching and are thus capable of satisfying the requirements involved in the treatment process. The after-treatment with a heavy-metal compound converts the dyestuifs at the end of the treatment into a form of considerably better fastness to light.

If certain metallizable dyestuffs fast to light were incorporated in the emulsion from the start, other properties of the material, such, for example, as is speed, would be substantially impaired. Moreover, the fastness to light of these rnetallized dyestuffs would be destroyed by certain steps involved in the treatment such, for example, as the use of strongly acidic treatment baths.

As will be realized from the foregoing it is possible to produce by way of the present invention by the silver dye bleach process color photographs that contain at least one heavy-metal compound of an azo dyestuff from which complex the metal is easy to eliminate in a strongly acidic medium.

In the silver dyestutf bleaching operation, the azo dyestuffs are reduced to ortho-hydroxyaminoaryl or orthodiaminoaryl compounds, and it is generally known that such ortho-disubstituted compounds are easily oxidizable. The largest possible quantity of the reduction product is obtained where the dyestuffs are completely bleached out and where the white parts of the image should be. As is also known, the ortho-hydroxyaminoand diamino compounds easily form colored oxidation compounds. It was to be expected that the treatment with metallizing agents would stain the color images and particularly in the parts which should be white. It is just here that the largest quantity of undesirable reduction products is to be found, and just here, too, that the colored oxidation products are the least tolerable. However, quite surpris ingly, no such staining takes place in the present process.

It is known to treat textile dyeings with certain agents yielding metal. It is also known to treat certain photographic materials, used in transfer processes, with metallizing agents. However, in the materials to be treated in accordance with these known methods no oxidizable orthohydroxyaminoand diamino compotunds are present.

Example 1 A film is coated with a gelatine layer containing per square meter 2.5 grams of silver as silver bromide, 0.6 gram of the yellow dyestuff of the formula:

OCH3 S OaNB and 1.0 gram of anhydro-biguanido benzyl alcohol acetate.

The film is exposed in contact with a stepped spectroscope wedge, developed in a metol-hydroquinone developer and fixed. The film is then treated in a dye bleaching bath containing per liter Hydrochloric acid of 36% strength cc Potassium bromide grams 100 Thiourea do 50 2:3-diaminophenazine milligrams 2 whereby the dyestuif is destroyed in the areas where metillie silver is present. The excess silver is oxidized in a bath containing per liter Copper sulfate grams 100 Sodium chloride do 100 Hydrochloric acid of 36% strength ..cc 100 and eliminated in a fixing bath. Between all baths and at the end the film is thoroughly rinsed.

A yellow color image obtained in this manner is aftertreated for 3 minutes in a solution consisting of Nickel sulfate grams 1.0 Monoethanolamine do 2.0 Water cc 100 Example 2 A film is cast which contains, instead of the dyestufi used in Example 1, the yellow dyestuif prepared by coupling on both sides tetrazotized benzidine-2:2'-disulfonic acid with 1-phenyl-3-methyl-5-pyrazolone. The film is de- G O-NH OH CH;

OHa-CO-NH veloped in identical manner and after-treated in an ammonical bath containing 10% of cobalt nitrate. When the film so after-treated is compared in a fadeometer or in sunlight with a film that has not been so after-treated but is otherwise identical, it is noticed that the after-treated film is very much faster to light than the film that has not been after-treated.

Example 3 The dyestuff of Example 1 is replaced by the magenta NEOaS NaOaS dyestufi obtained by coupling diazotized 1-amino-2-ethoxy- 70 benzene with 1-(para-acetylaminobenzoylamino)-8-hydroxy-naphthalene-3:6-disulfonic acid. In other respects the procedure of Example 1 is followed. After-treatment with the nickel bath of Example 1 or with the cobalt ably. Instead of the afore-mentioned after-treatment baths one of the following baths can be used with equal success:

Copper sulfate "grams" 1 Salicylic acid o 0.5 Water c 100 Sodium carbonate to raise the pH value to 4.3.

Copper sulfate grams 2 Monoethanolamine do 2 Water cc 100 Copper sulfate grams 1 Ammonia (28% strength) cc 2 Water cc 100 Copper sulfate grams 2 Salicylic acid do 1 Water 100 Sodium carbonate to raise the pH value to 4.3. Anhydro-biguanido benzyl alcohol acetate grams 1 Example 4 The dyestufi of the formula:

SOaH

is dissolved in water, the solution is added to a silver bromide emulsion in gelatine and cast as a layer. Exposure and development are as described in Example 1. After-treatment in one of the aforementioned baths, for example in bath (B) of Example 3, improves the fastness to light substantially.

Example 5 The dyestulf of the formula:

I S OaNa (obtained by coupling tetrazotized 3:3'-dihydroxy-4:4- diaminodiphenyl with l-amino-8-hydroxynaphthalene-2: 4-disulfonic acid in the presence of calcium hydroxide and pyridine) is dissolved in gelatine and rendered fast to diffusion, for example with anhydro-biguanido benzyl albath of Example 2 improves the fastness to light consider- 75 cOhOl acetate. When this dyestuff is used in the usual manner in the silver dye bleach process it produces a blue What is claimed is: component image which becomes fast to light on after- 1. In a process for making color photographs by silver treatment in a bath containing copper acetate, for example dye bleach method wherein a color image-containing mafor 30 minutes at 18 C. in a bath containing 30 grams of terial, having at least one gelatine layer containing metalcrystalline copper acetate dissolved per liter of water. lizable azo dye and being resistant to diffusion, is freed Instead of the copper acetate solution there may be from metallic silver by oxidation, the improvement comused a solution of sodium copper acetate or glycine copprising treating said material subsequent to said oxidation per having an equal content of copper. A similar imwith water-soluble compound of metal having an atomic provement in the fastness to light is also achieved by using number of at least 24 and at most 29 in aqueous medium instead of the copper acetate solution a solution that conf H 3, 5 to 11,5, tfiins to grams of Potassium titanium Sulfate P 10 2. In a process for making color photographs by silver of Waterdye bleach method wherein a color image-containing ma- Example 6 terial, having at least one gelatine layer containing metalhe dyestufi specified in Example 5 may be replaced lizable azo dye with at least one salicylic acid group and by the dyestufl of the formula: being resistant to dillusion, is freed from metallic silver O-GHz-COOH By using a copper salt according to Example 5 or cadby oxidation, the improvement comprising treating said mium acetate, cobalt acetate or nickel acetate, a greenish material subsequent to said oxidation with water-soluble blue image is obtained which is fast to light. compound of metal having an atomic number of at least A blue image fast to light is also obtained by after- 27 and at most 29 in aqueous medium of pH 3.5 to 11.5. treating with a copper salt, a nickel salt or basic chro- 30 3. In a process for making color photographs by silver mium sulfate, with the dyestuff of the formula: dye bleach method wherein a color image-containing ma- -Red images fast to light are obtained with the dyestuffs terial having at least one gelatine layer containing metal of the formulae: lizable azo dye with at least one hydroxyl group in vicinal Naois HN-OC 3N= on (1700B: HO

by after-treatment with a salt of manganese, cobalt or position to said azo group and being resistant to diffusion, nickel. is freed from metallic silver by oxidation, the improvement Examp 7 comprising treating said material subsequent to said oxida- On a film four gelatine layers are cast in the following tion with water-soluble compound of metal having an order of succession: atomic number of at least 27 and at most 29 in aqueous (1) A red-sensitive silver bromide emulsion containing medium f PH 35 to a dyestuff according to Colour Index Direct Green 27, as well as anhydro-biguanido benzyl alcohol acetate.

(2) A green-sensitive layer containing the additives specified in Example 3.

3 A ellow filter la er. 7O s E Aynomsensifizedy layer Containing the additives posit on to one nitrogen atom of said azo group and a mentioned in Example L group capable of forming complex metal compound to- The film is treated as described in Example 1. Aftergather Wlth Sald hydroxyl group m vlclnal p wn to the treatment with the nickel bath described in Example 1 other Hitmgen atom and being resistant to diffusion, is considerably improves the fastness to light of all dyestuffs. freed from metallic silver by oxidation, the improvement 4. In a process for making color photographs by silver dye bleach method wherein a color-image containing material having at least one gelatine layer containing metallizable azo dye, said dye having hydroxyl group in vicinal comprising treating said material subsequent to said oxidation With water-soluble compound of metal having an atomic number of at least 27 and at most 29 in aqueous medium of pH 3.5 to 11.5.

5. Process of claim 1 wherein said metal is present in said aqueous medium as a complex ion.

6. Process of claim 1 wherein said compound is monocyclic ortho-hydrocarboxylic acid of the benzene series.

7. Process of claim 1 wherein said compound is an amine.

8. Process of claim 1 wherein said metal has an atomic number of 27 to 29.

10 References Cited UNITED STATES PATENTS FOREIGN PATENTS 7/1956 Great Britain.

I. TRAVIS BROWN, Primary Examiner.

US. Cl. X.R. 

